The present invention relates to a device and method for determining the moisture content of material which is held on a bobbin or cone and, more particularly, to a device and method for determining the moisture content of non-homogeneous material held in a structure which contains a hollow core. Many different types of synthetic and organic materials are the basis for the construction of many different manufactured products. These materials must be gathered, transported and stored before being used in the manufacturing process. The manufacturing process itself may require multiple procedures, first to prepare the raw material, and then to use the processed material in the formation of the actual product. Many of these procedures are dependent upon the moisture content of the material. If the moisture content is too high, for example, the material may decompose during storage and transportation, before it can be used. If the moisture content is too low, processing and use of the material may be difficult.
Synthetic and organic materials whose behavior depends upon their moisture content include cotton, paper, wool, seeds, pharmaceuticals and synthetic fibers. As an example, cotton can be considered, although it will be appreciated that similar examples could be given for any of the above materials. Cotton is processed to separate the desired cotton from contaminating materials such as seeds, and is then spun into fibers for use in textile manufacture. For such processing and spinning to be successful, the cotton fibers should have an even moisture content that is neither too high nor too low. For example, fibers with low moisture content are weaker, breaking more frequently.
The optimum moisture content of the cotton fibers for the production of textiles is from 6.5 to 8% before spinning and between 6-10% on the cones or bobbins, depending upon the requirements of the subsequent processing steps. Thus, effective moisture control in the textile mill depends upon accurate measurement of the moisture content of the fibers.
The internal structure of the bobbin itself presents difficulties for measuring the moisture of material wrapped around it. The layers of the fibers around the bobbin frequently are not parallel, which can artifactually alter the behavior of the transmitted beam, and hence the apparent moisture content of the bobbin. Thus, the internal structure of the bobbin must be compensated for during calculation of the moisture content of the material.
In order to compensate for all of these potential measurement artefacts, moisture measurements may be performed using microwave radiation. Typically, a microwave radiation source is located on one side of the cotton bobbin, and an antenna is located on the opposite side of the bobbin. The radiation source beam is transmitted through a portion of the bobbin and is received by the receiving antenna, which then produces a signal. This signal is used to determine the moisture content of that portion of the bobbin and the mass uniformity of the bobbin. A method for performing such moisture measurements is disclosed in U.S. Pat. No. 5,621,330, referenced herein as if incorporated in full.
However, such measurements are difficult to perform because of the structure of the bobbin itself. Cotton bobbins typically have a hollow core. This hollow core significantly interferes with measurements made by microwave radiation and reduces the effectiveness of prior art devices and methods. Furthermore, cotton fibers on bobbins still have many irregularities of internal structure of the fibers themselves, making measurements of the moisture significantly more difficult. Hereinafter, the term "bobbin" refers to a structure of substantially any three-dimensional shape which has a hollow core.
Of course, cotton is not the only material to be transported, stored and processed on bobbins. Paper, pharmaceuticals, wool fibers, silk fibers and synthetic fibers are also necessary synthetic and organic materials which form the basis of many different products. Each of these materials may also be transported and stored on bobbins. The moisture content of each can affect processing, storage and manufacture. Furthermore, each of these materials forms different structures. That is, a bobbin of paper may have a very different internal structure from a bobbin of cotton. Thus, a moisture measuring device must be able to compensate for the effect of all of these different types of structures on the measured moisture content.
There is thus a widely recognized need for, and it would be highly advantageous to have, a device for measuring the moisture content of a bobbin of material, which can compensate for the hollow core of the bobbin, which can also determine the internal structure of the material and which is capable of adjusting such measurements for the material itself.